1. Field of the invention
The present invention relates generally to heating devices that utilize waste oil as fuel, and more particularly to such heating devices that use waste oil as a sole fuel source, that pre-heat the waste oil prior to burning and that mix the oil with pressurized air prior to combustion thereof.
2. Background
Combustion of waste oil, and in particular drain oil as is generated by automotive and other internal combustion engines, is considered a highly desirable means of disposal of such used lubricants. Efficient combustion promises the generation of heat energy for space heating and the safe elimination of a substance considered hazardous by the United States Environmental Protection Agency. Thus, various heaters or furnaces having the ability to burn waste oil have been proposed. However, the successful combustion of waste oil, such as drain oil, presents formidable hurdles. In particular, waste lubricants contains a wide variety of contaminants, such as, unburned fuel, water, acids, and particulate matter, such as, road dirt and dust, and metal particles resulting from engine wear. These impurities can result in the clogging of standard oil furnace burning nozzles and in the production of non-flammable gasses, both of which occurrences can stop combustion. In addition, waste automotive oil is of a high viscosity as compared with standard fuel oil, thus, it is more difficult to inject into a combustion chamber from a nozzle as a fine well aerated spray.
Initial attempts at burning waste oil involved increasing the pumping force applied to the oil to compensate for its increased viscosity, however, the force needed was very high, and the small nozzle apertures would ultimately become clogged. Other efforts involving simply increasing the nozzle aperture would result in reduced clogging, but would also greatly reduce combustion efficiency as the oil would not be atomized sufficiently. Current art waste oil burners, as seen generally in U.S. Pat. Nos. 4,162,887 to Grey, 4,249,885 to Reich and 4,487,571 to Robertson et. al., include the use of electrical heaters in the oil storage tank or fuel lines thereof to reduce oil viscosity, and filters to remove particulate matter. Also, this prior art shows the use of nozzles, such as made by Delavan, Inc., wherein compressed air is introduced within the nozzle and which mixes with the oil in a circumferential or swirling motion just prior to injection of the oil into the combustion chamber. This compressed air serves to better aerate and atomize the oil as well as resist blockage of the nozzle aperture. The prior art also describes the use of a second source of compressed air exterior of the nozzle to provide for combustion of the oil, as the atomizing oil is not sufficient for this purpose. In addition, as seen in French patent No. 75 05928 to Poirier, heated waste oil can be circulated through the gun prior to combustion so that the oil and gun first reach optimal temperature to insure proper fluidity of the oil.
However, current art waste oil burners continue to be plagued by the problem of flame outage. Such outage, and thus, burner unit shut down, is primarily the result of nozzle orifice blockage by particulate matter or agglomeration of the oil, or as the result of essentially inflammable gasses being periodically ejected from the nozzle in place of the oil. Thus, the reliability of such systems is quite low as they require frequent cleaning and repair. Therefore, such systems can not be left unattended without a back-up heating system.
Accordingly, it would be highly desirable to have a heating system capable of burning waste oil in a manner that is efficient and reliable.